AnsweredAssumed Answered

SOLT User Defined Cal Kit: Offset Loss issue

Question asked by SOLT_guy on May 30, 2009
Latest reply on Jul 19, 2009 by SOLT_guy
Dear Sir:

     I have a question about calculating the offset loss value which is to be input into a VNA user defined cal kit (I use a 8753C NA).

      I have read many application notes on the subject of  - user defined "vector network analyzer" calibration kits - and I have determined that the offset loss equation is in contradiction with respect to many sources (not only Agilent sources but third party vendors, consultants, etc.). The Agilent AN notes which set forth the offset loss equation are not well "specified". 

      These two application notes appear to set forth consistent offset loss equations:


"Calibrating Standards for In-Fixture Device Characterization"

"Specifying Calibration Standards for the Agilent 8510  Network Analyzer"


This application note appears to set forth an inconsistent offset loss equation:


"De-embedding and Embedding S-Parameter Networks Using a Vector Network Analyzer"


This application note attempts to specify the linear magnitude definition of offset loss  but fails to specify the offset loss equations in dB clearly.


"Specifying Calibration Standards and Kits for Agilent Vector Network Analyzers", Application Note 1287-11.


      Let's start with AN 1287-11 since the equations probably can be derived from the original S-parameter models which were developed in the 1970's.

      The linear offset loss equation with respect to S21 data has a constant of 2 in the equation.  Can you tell me how the 2 is derived in this equation (if the derivation is too long then please set forth the critical points in the derivation and then point to the references which substanciate these critical points)?

       In AN 1287-11 the log-magnitude offset loss equations are not well specified at all for S21 or S11 data.  For example:

[ ( -ln (10) db 1 Ghz ) / 10 ];

this term makes no sense (and I do understand that a 1 Ghz S21 measurement is being made).  In reply, please specify this equation in a mathematically understandable format and please explain where to insert the S21 measurement in the equation.

       In reply,  for the sake of clarity and consistency, please take a hypothetical S21 measurement and insert it into the linear offset loss equation and then set forth the calculated output which is to be input into the user defined calibration kit.  After this, please take this calculated value and show a mathematical conversion from the linear offset loss equation to the log magnitude offset loss equation in a format such that if I take that that same S21 value and insert it directly into the the log magnitude equation you will be setting forth in your reply,  I will get the same result.  It is important that you reply in this manner because from your reply answers I will test the consistency of the other equations found in the other Agilent application notes set forth.

      Thank you for your courtesy and I look forward to hearing your reply.  

Outcomes